The first trophic level, primary producers, holds the most biomass on Earth by an enormous margin. Plants alone account for roughly 450 of the estimated 550 gigatons of carbon in all living things, about 80% of the total. Every level above producers, from herbivores to top predators, contains dramatically less living material. This pattern holds true across most ecosystems, though oceans are a fascinating exception.
Why Producers Dominate
Energy flows through an ecosystem like a leaky pipeline. When a rabbit eats grass, it doesn’t convert all that plant energy into rabbit tissue. A large portion is burned off as body heat, used for movement, or lost as waste. The commonly cited rule of thumb is that only about 10% of the energy consumed at one trophic level becomes available to the next. That number is approximate and varies between ecosystems, but it captures the basic reality: each step up the food chain means a steep drop in available energy.
Less energy means less total living material can be supported. A grassland might sustain thousands of kilograms of plant matter per hectare, hundreds of kilograms of herbivores, and only a few kilograms of top predators. This creates the classic “biomass pyramid,” wide at the base and narrow at the top. The pattern also limits how many trophic levels an ecosystem can sustain. Most food chains top out at four or five levels because there simply isn’t enough energy left to support a sixth.
The Scale of the Gap
The numbers are staggering when you look at the whole planet. A landmark census published in the Proceedings of the National Academy of Sciences estimated total global biomass at about 550 gigatons of carbon. Plants, nearly all of them land-based, make up roughly 450 gigatons. Land biomass overall sits around 470 gigatons of carbon, while the entire ocean contains only about 6 gigatons. Trees, shrubs, and grasses don’t just outweigh animals; they outweigh everything else on Earth combined several times over.
Most of that plant mass is structural tissue: wood, bark, roots. A single large tree can weigh several tons, and forests cover about 30% of Earth’s land surface. The sheer physical bulk of terrestrial vegetation is the main reason the first trophic level so thoroughly dominates global biomass figures.
Why Oceans Break the Pattern
If you look only at the open ocean, the picture flips. Marine primary producers are mostly phytoplankton, single-celled organisms that are individually tiny and live for just days. Their turnover rate is roughly 1,000 times faster than forests and about 100 times faster than grasslands. Phytoplankton grow, get eaten, and are replaced so quickly that at any given snapshot in time, their total standing biomass can be smaller than the biomass of the animals feeding on them.
This creates what ecologists call an inverted biomass pyramid. The base of the food web appears to weigh less than the levels above it, which seems like it should be impossible. The key is the difference between how much living material exists at one moment (standing biomass) and how much is being produced over time (productivity). Phytoplankton may have low standing biomass, but their production rate is extraordinary. They generate new cells so fast that they can feed a much larger mass of zooplankton and fish above them.
Inverted pyramids also show up in specific habitats like kelp forests, where researchers have found four to five times more biomass in large fish than in small ones. In those cases, the explanation often involves mobile predators that travel between habitats, importing energy from elsewhere. The local pyramid looks inverted because the consumers aren’t surviving solely on what’s produced within that patch of reef.
Standing Biomass vs. Productivity
This distinction between standing biomass and productivity is the single most important concept for understanding trophic-level biomass. A redwood tree locks carbon into wood that persists for centuries. A phytoplankton cell converts sunlight to carbon, gets consumed within days, and is replaced by a new cell. Both are primary producers, but one accumulates mass while the other cycles it.
Phytoplankton lack the heavy structural tissues that make trees so massive. They’re small, nutritious, and easy for herbivores to digest, meaning a greater fraction of their energy actually transfers up the food chain. Aquatic food webs tend to be more efficient than terrestrial ones partly for this reason. Consumers get more nutritional value from eating tiny, fast-growing organisms than from chewing through bark and cellulose.
On land, where plants build wood and roots that persist for decades or centuries, standing biomass piles up at the producer level. In water, where producers are microscopic and short-lived, biomass is more evenly distributed or even top-heavy. Both systems still obey the same thermodynamic rules. Energy is still lost at each transfer. The difference is simply how long that energy stays locked in living tissue before moving on.
How This Plays Out Across Ecosystems
In a tropical rainforest, plant biomass can exceed 200 tons of carbon per hectare. The animals living in that forest, from insects to jaguars, represent a tiny fraction of that figure. Grasslands show the same pattern, though the gap is smaller because grasses store less structural material than trees.
Coral reefs sit somewhere in between. They have high productivity and complex food webs, but the physical structure of the reef itself (built by coral animals over decades) adds consumer biomass in ways that make simple pyramid models less tidy. Freshwater lakes and rivers generally follow the terrestrial pattern, with algae and aquatic plants outweighing the animals they support, though small, productive ponds can occasionally show inverted pyramids similar to open-ocean systems.
The bottom line: across Earth as a whole, and in the vast majority of individual ecosystems, the first trophic level holds the most biomass. The exceptions in marine and some aquatic systems are real and important, but they reflect the unusual speed of phytoplankton reproduction rather than a violation of energy transfer rules. When you account for productivity over time instead of a single snapshot, producers still supply more total energy than any level above them, everywhere on the planet.